AsyncRequestGroup.swift

import Foundation
import HTTP
import Dispatch

public class AsyncRequestGroup {
    
    private enum DummyError: Error {
        case dummy
    }
    
    public typealias RequestTask = () throws -> Response
    
    public static func execute(tasks: [RequestTask]) -> [Result<Response>] {
        let lock = Lock()
        let group = DispatchGroup()
        
        var results = [Result<Response>]()
        
        for _ in tasks {
            results.append(Result.failure(DummyError.dummy))
        }
        
        for i in 0..<tasks.count {
            group.enter()
            let task = tasks[i]
            DispatchQueue.global().async {
                do {
                    let response = try task()
                    lock.locked(closure: { 
                        results[i] = Result.success(response)
                    })
                } catch {
                    lock.locked(closure: {
                        results[i] = Result.failure(error)
                    })
                }
                group.leave()
            }
        }
        
        group.wait()
        return results
    }
}